Transportation systems are relied on to move people and goods (cargo) from one location to another location. Over the years, transportation systems have developed from simple isolated collections of streets to more robust systems. Modern transportation systems include many interconnected streets, roads, and highways that form integrated local, state and interstate highway systems.
These systems are often designed to seamlessly function together to promote the efficient flow of traffic. However, due to the ubiquity of vehicles and the ever-increasing demand imposed on the transportation system by countless individuals, businesses and other organizations, modern transportation systems have become increasingly congested with vehicle traffic. Poor traffic controls exacerbate the problem associated with congestion. Further, congestion is particularly problematic in metropolitan areas where there typically exist an enormous number of vehicles within the transportation system at any given time. These problems are further heightened during the morning and evening commutes, holidays, and during special events such as sporting events, concerts, and the like where the concentration of vehicles in a region quickly burgeons. This congestion results in enormous inefficiency including long delays, increased fuel costs, bottlenecks, elevated pollution levels (from engine exhaust), increased accident rates, high driver stress, and a generally negative impact on communities.
These inefficiencies have challenged engineers and planners to design transportation systems including associated traffic controls that permit an optimal flow of vehicles. A further challenge is presented because a system that is optimal for some time periods may be far from optimal during other time periods, e.g., during commute times, special events, or on particular days.